Threat Bulletin 1370: Slowloris against a healthcare portal platform in the Nordics

On Sunday 24 May 2026 at 23:13 UTC, a Slowloris targeted a healthcare portal customer in the Nordics. The attack peaked at 709.7 million requests per second and lasted 78 minutes. Traffic originated from 75 autonomous systems in 61 countries, predominantly a headless-browser farm.

Vector Slowloris
Peak 709.7 million requests per second
Duration 78 min
Time to mitigation 0.899 s
Attack traffic reaching origin 0.083%
Legitimate traffic challenged 0.61%

Timeline

The attack was preceded by an extortion email received two days earlier. Request rates on the targeted routes exceeded their hourly baseline by a factor of 152 within 13 seconds. The risk score of participating clients crossed the challenge threshold automatically and proof-of-work difficulty rose with origin load.

What the customer saw

Checkout conversion was unchanged compared with the same hour of the previous week.

Recommendations

  • Keep origin IPs out of public DNS history.
  • Enable log streaming to your SIEM for faster correlation.
  • Review allow-listed partner ranges quarterly.

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